Exploring the potential of Eu3+ and Mn4+ activated LaAlO3 phosphors as red and far-red emitters for horticulture lighting

Abstract

The development of efficient red and far-red emitters, for efficient plant absorption in the Photosynthetically Active Radiation (PAR) region, holds significance in contemporary plant growth control. This study focuses on the synthesis and characterization of LaAlO₃ as a host material, doped with Eu³⁺ and Mn⁴⁺ ions, using a solid-state reaction method. The investigation encompasses the creation and analysis of both single-doped and co-doped samples, employing techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy. XRD analysis consistently confirmed the perovskite-like structure of all samples, devoid of detectable impurities or major structural changes due to doping. SEM images revealed a uniform distribution of regularly shaped particles for the co-doped sample. The PL spectroscopy showed that the doping led to strong photoluminescence, with the co-doped sample exhibiting the intensity of each of the ions independently neither exhibiting quenching nor energy transfer mechanisms. The excitation spectrum of Eu³⁺ exhibited a broad charge transfer band at approximately 328 nm, coupled with characteristic f–f excitation bands. On the other hand, the Mn⁴⁺ ion's excitation spectrum featured transitions from ground state (4A_2g) electrons excited to higher excited states (4T_1g, 2T_2g, and 4T_2g) centered at 350 nm and within the region 250–550 nm. The co-doped sample was excited at a common excitation wavelength of 460 nm and underwent an in-depth examination of its photoluminescent properties, including decay curves analysis and time dependence also. The results from this study suggest that the synthesized phosphor materials exhibit substantial potential for diverse applications, including but not limited to solid-state lighting for efficient plant growth.